J-chain is an acidic 15-kDa polypeptide, which is associated with pentameric IgM and dimeric IgA via disulfide bonds involving the penultimate cysteine residue in the 18-amino acid secretory tail-piece (tp) at the C-terminus of the IgM μ or IgA α heavy chain. The three disulfide bridges are formed between Cys 12 and 100, Cys 71 and 91, and Cys 108 and 133, respectively. See, e.g., Frutiger et al. 1992, Biochemistry 31, 12643-12647. Structural requirements for incorporation of the J-chain into human IgM and IgA and for polymeric immunoglobulin assembly and association with the J-chain are reported by Sorensen et al. 2000, Int. Immunol. 12(1): 19-27 and Yoo et al. 1999, J. Biol. Chem. 274(47):33771-33777, respectively. Recombinant production of soluble J-chain in E. coli is reported by Redwan et al. 2006, Human Antibodies 15:95-102.
Methods for making hybrid IgA/IgG and IgM/IgG antibodies are known in the art. Thus, recombinant production of hybrid IgA2/IgG1 antibodies is reported in Chintalacharuvu et al. 2001, Clin Immunol 101(1):21-31. It has been reported that addition of αtp or μtp at the end of IgG γ heavy chain facilitates polymerization and enhances effector function such as complement activation (Smith et al., J Immunol 1995, 154:2226-2236). The IgA/IgG hybrid antibodies possess properties of both IgA and IgG. Methods for recombinant production of IgM antibodies are also known in the art. E.g., Tchoudakova A, et al., High level expression of functional human IgMs in human PER.C6 cells. mAbs. 2009; 1(2):163-171.
Despite the advances made in the design of antibodies, there remains a need for modified antibodies with improved properties, such as improved affinity, specificity and/or avidity, as well as the ability to bind to multiple binding targets.
As the field has progressed, antibody function has been enhanced through creative means of protein engineering, such as to provide higher affinity, longer half-life, and/or better tissue distribution, as well as combination of small and large molecule technologies for increased focus of cell destruction via toxic payload delivery (e.g., antibody-drug conjugates). Another approach to improving antibody function takes advantage of the bivalent binding of the immunoglobulin G (IgG) structure which allows one IgG molecule to bind two antigens. Indeed, in certain applications, there exists good potential for asymmetric antibodies to exert useful functions by simultaneously binding two different target antigens. To address this need, a variety of constructs have been produced to yield a single molecule that can bind two different antigens, allowing for functions never before seen in nature. An example of this bi-specific approach is “blinatumomab” (MT103 or AMG103) which binds the CD3 and CD19 receptors, on T- and B-cells, respectively. This tethering of a cytotoxic T-cell to a cancerous B-cell, allows for effective treatment of B-cell leukemia.
The blockade of immune checkpoints has emerged as a promising area for the advancement of cancer treatment. Immune checkpoints refer to inhibitory signaling pathways that are encoded into the immune system, and which play a vital role in maintaining self-tolerance, as well as modulating the duration and amplitude of immune responses. See, e.g., Pardoll, Drew M. “The blockade of immune checkpoints in cancer immunotherapy.” Nature Reviews Cancer 12.4 (2012): 252-264; Postow, Michael A. et al., “Immune Checkpoint Blockade in Cancer Therapy,” J Clin Oncol. 2015 Jun. 10; 33(17):1974-82. doi: 10.1200/JCO.2014.59.4358.
Despite positive proof of concept results in preclinical models, investigators have reported that monoclonal IgG blocking antibodies directed against T-cell inhibitory signaling pathway components (for example, ipilimumab (Bristol-Myers Squibb) and tremelimumab (Medlmmune/AstraZenica), both directed against CTLA4) have only achieved minimal efficacy results in a clinical setting. E.g., Postow et al., pp. 1-2. In addition, treatments involving monoclonal IgG antibodies have resulted in immune-related adverse events, such as dermatologic, GI, hepatic, endocrine and other inflammatory events. E.g., Id. at p.4. As such, the use of monoclonal IgG antibodies in immune checkpoint blockade may be limited by the therapeutic index of such molecules, in that the dose of a monoclonal IgG antibody required to elicit the desired therapeutic effect also causes immune-related adverse events.
Accordingly, there is a need for binding molecules with increased avidity that will provide increased potency so that lower dosage levels can be used, thereby preventing the occurrence of immune-related adverse events, while still achieving effective blockade of T-cell inhibitory signaling pathways.
The pharmacokinetics and pharmacodynamics of monoclonal antibodies are complex, and depend on both the structure of the monoclonal antibody, as well as the physiological system that it targets. Moreover, different antibody classes are typically processed within a subject via different cellular and physiological systems. For example, secretion into the bile is an important pathway of elimination for IgA antibodies, whereas this route is not a significant contributor to the elimination of IgG antibodies. Rather, the majority of IgG elimination occurs via intracellular catabolism, following fluid-phase or receptor-mediated endocytosis. E.g., Wang et al., Nature 84:5 (2008). Furthermore, full-length IgG antibodies have been shown to be primarily distributed within the blood stream, while smaller IgG antibody fragments appear to distribute within the extra-vascular space to a greater extent. E.g., Tabrizi et al., AAPS J. 2010 March; 12(1): 33-43. The blood brain barrier generally prevents immunoglobulin molecules from entering the central nervous system via the circulation. E.g., Yu et al., Science Translational Medicine 16:261 (2014). Furthermore, immunoglobulins that are directly injected into an extra-vascular space, such as the eyeball, typically only remain in the space on the order of hours. See., e.g., Mordenti, J. et al., Toxicological Sciences 52, 101-106 (1999); Mordenti, J. et al., Toxicological Sciences 27(5), 536-544 (1999). As such, control and manipulation of factors that influence the absorption, distribution, metabolism and/or excretion (ADME) characteristics of monoclonal antibodies is an important consideration when designing a therapeutic antibody composition.
Accordingly, there is a need for binding molecules whose ADME characteristics can be controlled and modulated to achieve a desired therapeutic effect.